Automatic telephone system



3 Sheets-Sheet l fA/vfn/roR- OSCAR 0 LEVY AUTOMATIC TELEPHONE SYSTEM Filed Oct. 9, 1953 Aug. 25, 1.936.

Aug.25,1936. o@ LEVY 2,052,05

AUTOMAT I C TELEPHONE SYSTEM Aug. 25, 1936.l 0, C, LEVY Y AUTOMATIC TELEPHONE SYSTEM Filed Oct. 9, 1933 3 Sheets-Sheet 3 Patented Aug. 25, 1936 PATENT oF-.FlcE

AUTOMATIC TELErHoNE` i SYSTEM Oscar C.'Levy, Chicago, Ill., assignor vto Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application October 9, 1933,-Seria1 No. 692,717

20 Claims.

This invention relates in general to automatic telephone systems, and more particularly to 'small private installations, and its principal object is to provide a common talking, selective l v5 ringing system which is an improvement over the one described in Patent No. 1,681,703, issued to .C. E Lomax on August 21, 1928. More specifically, the principal object of the invention is to provide an efficient-yet inexpensive system for l` private installations, comprising a common talking .line with .a plurality of substations thereon.

Another object of the invention is .the provision of a .common .talking circuit `over which :l two .groups of subscribers lines may talk. This common talking circuit is so arranged that it maybe. divided into two parts in telephone con- Znections involving subscribers of the same group, `one .part serving .for connections between subscribers in onegroup and the other part serving .for connections between subscribers in the other group. This arrangement permits a second call te` beset up between subscribers in the second group after a callhasbeen setup between sub- .scribers in the .first group.

Another object of the invention is the provision `of an automatic stepping circuit for a .switch `serving two groups of lines to enable such switch to be automatically advanced beyond one Vgroup of lines .when va digit greater than a predetermined Anumber is dialled .on .a preceding switch before the switch is, itself, directively operated on a succeeding digit. This arrangement allows the switch to complete its rotating movement. beyond the group of lines during the first .digit .and theintervalbefore the succeeding digit is received.

The means by which the foregoing and other objects are accomplished will be fully set forth hereinafter, reference being made to the accompanying drawings, comprising Figs. 1 to 5, in-

elusive.

Referring to Fig. 1, two groups of subscribers lines and the two suitable common talking paths 4i5 comprising conductors and 2 and conductors 3 andd are shown, The iirst group comprising fty stations, such as SS| to SS3, inclusive, will, for convenience, be called the secret service lines and would, for example, include the different executives telephones and the telephones of the ofiice help in,V a factory. The second group comprises, inthis case, only forty stations, such as OSI to OSS, inclusive, and will be called the ordinary service lines.

and motor magnet 2|3.

The ordinary service .-55 lines would, for example, include the telephones assigned to the diierent departments of the factory. In `both groups each substation is provided with a standard, Well known automatic telephone set, comprising the usual receiver and transmitter, induction coil, calling device, `and 5 ringer. All of `the secret service lines are connected totalking conductors lk and 2 and all of the ordinary service `lines are connected to the talking conductors 3 and 4. Each subscriber has anindividual ringing lead which terminates 10 in'its allotedbank contact inthe banks of the connector C shown in Fig. 3.

In Fig. 2 isshown a group of relays` and a ringing machine which are controlled byy both groups of Vsubscribers in establishing telephone l5 connections. Lamps, such as `lamp |64, are pro- .vided if desired and located at different visible points throughout the establishment for indicating when thecommon talking circuit is inuse ,by ordinary service subscribers. In a similar 20 manner the lamp |65.and other lamps located throughout the establishment indicatelwhen the ,common talking circuit is used by secret service subscribers lines.

In the left hand portion of Fig. 3is shown a 25 so-called minor switch .M comprising wipers 203v and 204, motor ,magnet `'205, release magnet 200, and off normal springs 20| and '202. The wipers of the switch M are connected as shown and are rotated upon ,the energization of thestepping 30 magnet 205 andreleased'to normal position by spring tension in response to the release magnet 206 withdrawing the holding detent from its ratchet (not shown). Off normal springs 20| .and 202 are shown in normal position and are 35 closed as soon asthe wipers are moved off normal.

Near the center-of Fig. Y3 is shown the connector C comprising Wipers 201 to 2|2, inclusive,

The mechanical con- 40 struction of connector C is similar to the wellknown 25-point rotary line switch commonly used in automatic telephonesystems, in which .thewipers are advanced in a forward direction onlyon the `deenergization of the motor magnet. ,45

` The `first ten bank contacts accessible to wipers 20'! to 2| I, inclusive, are connected to the individualringing leads of the secret service lines, the eleventh bank contacts accessible to these Vwipers are left dead, while the twelfth to twenty- 50 rst bank vcontacts accessible to these wipers are connected to the individual ringing leads of the Vordinary service lines and to the banks of the code call switch CC as shown. The wiper 2| 2 and its associated bank contacts are for control- Y5,5

ling the automatic operation of the motor magnet 2|3.

The code call switch CC is similar in mechancal construction to the connector C and comprises wipers 230 to 232, inclusive, and motor magnet 235. The minor switch MI is mechanically similar to the minor switch M and comprises the wiper 240, stepping magnet 24|, release magnet 242, and off normal springs 243. The relays 25| to 255, inclusive, in connection with the code call switch CC and minor switch MI control the circuits for ringing the code call bells 21|, 212, etc., located throughout the establishment or factory at different locations.

Fig. 4 shows a group of manual telephone stations, such as CI to C3, a relay group R, and a master telephone station MS, which are to be substituted for the ordinary service lines of Fig. 1 when master station service is desired. When Fig. 4 is being used the dotted jumpers 45 and 46 are connected to the talking conductors 3 and 4 and the full line jumpers 43 and 44 of the ordinary service lines are cut. Each manual substation comprises the usual receiver, transmitter, induction coil, ringer, and an individual ringing lead which is connected to the banks of the connector C in place of the ordinary subscribers individual ringing leads. The master telephone station MS is a standard automatic substation similar to substation SSI, having, however, an eXtra ringer. The individual ringing lead of station MS also terminates in the bank of the connector C in accordance with the number assigned thereto.

Referring to Fig. 5, the substations A and AI are of the usual manual type and are located at the same places as the automatic substations SSI and SSZ of Fig. 1. The line of substation A, when calling is connected with the line of substation AI, or vice versa, by the relay group R. The

relay group R is similar to relay group R' of Fig.

4 with the exception that the relay 14 and its connections have been omitted from group R', and it will be seen that either direct line service or master station service can be given whenever this relay group is provided.

Having given a brief description of the apparatus, the operation of the same will now be explained in detail. For this purpose it will be assumed that the subscriber at station SSI desires to call the subscriber at SSZ. Subscriber SSI will remove his receiver and listen to see if a common talking line is in use. In response to the removal of the receiver line relay |04 is energized over the following circuit: from ground through the lower winding of relay |04, resting contact and armature IIS, conductor 2, through the calling substation loop to conductor I, armature I I8 and its resting contact, and through the upper winding of relay |04 to battery. At armature |23 relay |04 completes an obvious energizing circuit for release relay |05. Relay |05 upon energizing at armature |24 grounds release trunk conductor I 63 to light the lamps such as lamp |64 and at armature |25 prepares a point in the impulsing circuit.

Subscriber SSI now operates his calling device CD in accordance with the first digit of the called subscribers number. Line relay |04 deenergizes after each impulse transmitted and at armature |23 and its resting contact completes the impulsing circuit for relay |08 and rotary magnet 205 as follows: from ground by way of armature |23 and its resting contact, armature |25 and its working contact, through the normally closed springs controlled by armature |28 to conductor |52 where the circuit divides, one branch going through the winding of relay |08 to battery, and the other branch going through the winding of the rotary magnet 205 to battery. Relay |08 energizes over the above traced circuit to maintain its armature |93 attracted throughout the impulsing period, and at armature |93 and its resting contact opens a point in the circuit to motor magnet 2| 3, and at its working contact prepares a new impulsing circuit for relay |08 and magnet 205. Rotary magnet 205, upon energizing over the above-traced circuit, operates its pawl to advance the wipers 203 and 204 into engagement with their rst bank contacts. As soon as wipers 203 and 204 are moved off normal the off normal springs 20| and 202 close. Off normal springs 202 prepare a circuit for the release magnet 206 and the off normal springs 20| complete the energizing circuit from ground by way of conductor |53 for energizing the off normal relay |05. Relay |06, upon energizing, at armature |26 starts the ringing machine by energizing the vibrating relay Ill over the generator start lead |10. Relay I1| upon energizing operates its vibrating armature |12 to close springs |15. Springs |15, upon closing, complete a short circuit around the winding of relay |1| with the result that relay I 1| now deenergizes and releases its armature. When springs |15 open relay |1| again energizes and again operates its armature |12 to close springs |15 to short circuit relay 1|. In this manner the relay |1I vibrates its armature |12 as long as ground is connected to the generator start lead |10. At springs |13 and |14 vibrating arm |12 alternately connects ground to the upper and lower left hand windings of the ringing transformer RT.. Due to this alternate condition the right hand windings of the ringing transformer RT transmit ringing current out over the conductor |35 in the well known manner. At armature |21 relay |06 opens one point in the restoring circuit of the connector C at its resting contact, and at its working contact prepares a locking circuit for relay H0; at armature |28 opens the original impulsing circuit and completes a new impulsing circuit before the second pulse of the first digit is transmitted. The second impulse of the rst digit is transmitted from ground by way of armature |23 and its resting contact, armature |25 and its working contact, working contact and armature I 28, armature |93 and its working contact, and from thence through the winding of relay |58 to battery, and over conductor |52 through the winding of rotary magnet 205 to battery. The remaining impulses of this digit, if more than two, would be transmitted over the circuit just traced.

In this case since the subscriber SS2 is being called, the rst digit dialed is 1 corresponding to the first digit in the subscribers number, and therefore the wipers 203 and 204 come to rest in engagement with their rst bank contacts; the wiper 203 preparing a point in the ringing circuit and wiper 204 preparing a point in the circuit of relay |01. After the last impulse of the rst digit has been transmitted, line relay |04 is maintained energized and slow to release series relay |08 is deenergized after an interval. At armature |93 relay I 08 prepares an impulsing circuit to the motor magnet 2|3.

Subscriber SSI now operates the calling device CD in accordance with the second digit, in thi.c case the digit 3. Line relay |04 again follows the impulses and at each deenergization completes the following circuit for operating the rotary Caos-anso f series relay 09 and motor. magnet. `2.'| 3 as follows:

`"ground from armature |23 andtsrestingzcontact,

y armature |25 and its working contact, armature. v

circuit for itself frorngrounded armaturei|21;

`at armature|`32 prepares an venergizing circuit for ringing relay at .armature I |33-opens "the impulsing circuit now vclosedat armature |34;

`and at armatures .|534 and |35 opens points in theautomatic stepping circuitxoffthe connector C. lMotor vmagnet 2|3 energizes'and deenergizes for each `impulse received and on each deener- Agization thereof steps the wipers 21ato 2|2, in-

clusive, one step. -Since the digit dialled is 3, 'three impulses are transmitted to 'the motor l-magnetl'l-l, and the wipers 201 to 2|2, therefore, stop in engagement with'itheir third bank contacts, Where wiper 231 prepares the circuit for ringing subscriber SSZ over its individual ringing vlead |3 4terminating in the .third lbank contact `accessible to wiper 231. After the last impulse ofthisseries is transmitted line relay |34 is again gizes after aninterval.

energized and `slow to release zrelay A|33 Ideener- At armature |39 relay |09 opens the impulsing'circuit and at armature |29 and its working contact opens the original energizing circuit of relay I3, which relay is now "locked over armatures |21 and |3 and at its resting contact completes a circuit for energizing "ringing relay by way of armature |32. Relay energizes and starts the arm |31 vibrating "for-apredetermined time'tointermittently close Vfthe armature |33, at armature |33 prepares acircuit for relay l2, and at armature |38 completes `the-ringing circuit for ringing subscriber SSE as follows: from generator lead |80 b-y Wayof .armature V|92, armature |33, resting contact .and

"armaturei|42,armature |41, conductor |59, Wiper 243 in engagement with its iirst bank contact, Wiper 2 01 in engagement with its third bank contact, individual ringing conductor I3, through the `ringer and condenser at substation S82, conduc- `tor 2, armature H19 and resting contact, and ythrough the lower winding of relay |04 to ground. Relay ||3being a slow to operate relay will not voperatedts armature, while the arm |31 isvibrating and `intermittently operating armature 33. After a predetermined time arm |31 stops Vibrating and closes armature |35 long enoughto energize the ring cut off relay H3 vas follows: Vlirorn ground by way of resting contact and armature 14|, armature |36, andithrough thewinding of A-ring cut oii relay M3 to battery. At armature |45 relay i3 completes a locking circuit foritself from'grounded release trunk conductor |33, at armature |46 closes a circuit for energizing relay |02, at armature |41 opens the ringing circuit, and at armature |48 connects ground to release conductor |54. Relay |32 energizes over the following circuit: frorn grounded wiper 234, conductor |49,v armature |46, armature |25 and through the windingof relay |62 to battery. Re-

lay |92 upon energizing, at armature ||3com .pletes va circuit for energizing relay |31; at armature ||1 closes a temporary locking circuit for itself from grounded release trunk conductor "|53 fand by `Way of the normally closed y springs foon- -trolled-by-armature and at armaturesxll and |l9`disconnects the line relay |64 and connects theirelayllll in placethereof. 'The circuit for energizing :relay |01 may be vtraced from grounded wiper 234 in engagement with its .first bank contact,conductor |49, armature M5,- and through the ywinding of' relay |31 to battery. At .armature 9| relay |31 Vconnects conductor y|146 lto the upper winding of relay .|94 to Aprepare-a tone circuit for transmitting a-tone to ordinary :subscriberslines when such lines call the secret service lines ata time when the secret service lines are busy, and at 'armature |92 opens a `further 'point inthe ringing circuit. Relay ||l| is :now "energizedover the following circuit: fromground Uthroughthe lower -Windingof relay lill, Working contact and armature ||9,' conductor 2, vthrough the calling or called subscribers substation loop to conductor' and by way of armature |18 and its working contact through the upper winding of relay ||3| to battery. At armature ||4 relay |Il| grounds conductor |53 to illuminate all of the secret service lamps, such as |35, andat armature ||5 maintains the locking circuit of relay' |32 independent of Ithe grounded release v trunk conductor |63. Liner-clay |124 deenergizes when'its circuit is opened andat armature |23 opens the circuit of slowto release relay |05.

When ring cut oli relay 3 grounded release conductor |54 at armature |48, release magnet 206 of the switch M is energized by Wayof the closed off normal springs '232. 'Release magnet 294 upon energizing withdraws the holding detent from its ratchet (not shown) Vthereby per-v initting the wipers 203 and2l4 to be returned to normal position by spring tension at Vwhich time the 01T normal springs 20| and 202 are opened. In response to the restoration of Wiper 12M-the circuit of relay 4||l1 is opened-and said relay now deenergizes. The restoration of oli normal springs 252 opens the. circuit of off normal relay AH34, which likewise deenergizes. Relay |31 deenergizes and at armature |9| -opens a point -in the prepared tone circuit and at armature |92 lagain prepares a point in the ringing circuit. Relay !56, upon deenergizing, at armature |'disconnects ground from the generator start llead |13 to stopthe ringing machine, at armature |21 opens the locking circuit of relay El at its working contact, and at its resting contact grounds conductor |58 to prepare the restoring circuit for the connector C. Relaylllil deenergizes after its locking circuit is opened andai; armature l|32 opens the circuit of ringing relayvll -whichlikewise deenergizes, at armature |33 prepares a Vpoint in the irnpulsing circuit, at armature |34 prepares a point in the automatic stepping cir-v -cuit of connector C and at armature closes the restoring circuit ofthe connector C as follows: from grounded armature |35, conductor |59, throughqthe upper multipled contacts engaged by wiper 2|2, through the interrupter springs '1244, and through the winding of motor ymagnet to again interrupt its own circuit to cause. the wip-'r ers to step into engagement with their fifth bank contact. This automatic stepping circuit is completed as long as the wiper 2|2 engages the multipled contacts connected to grounded conductor |59. When wiper 2| 2 reaches its eleventh bank contact a new circuit is completed from grounded armature |21 and its resting contact, conductor |58 connected to the multipled contacts II to 24, inclusive. In the same manner as previously described the motor magnet 2|3 interrupts its own circuit to advance the wipers step by step until wiper 2|2 no longer encounters a grounded bank contact. The wipers of the connector C are therefore stepped into engagement with their twenty-fifth or off -normal position bank contacts, at which time wiper 2|2 no longer encounters a grounded bank contact. Ringing relay III deenergizes when its circuit is opened by relay I I and at armature |35 disconnects ground from conductor |40 to open the original energizing circuit to ring cut off relay I I3, and at armature |38 opens a point in the ringing circuit. Shortly after line relay |04 deenergizes slow to release relay |00 likewise deenergizes, and at armature |24 disconnects ground from conductor |63 to extinguish the lamps |04 and to open the locking circuit of ring cut off relay i I3 which deenergizes. Ring cut 01T relay ||3 at armature |41 again prepares the ringing circuit. All of the relays with the exception of relays IIlI and |02 are now in normal position and the wipers of both the minor switch M and the connector C are restored to their normal positions and may be used i'or establishing the ringing circuit for signalling an ordinary service line. The secret service lines receive talking battery through the upper and lower windings of relay IIlI and talk over the common talking conductors I and 2. By the operation of relay |02 it can be seen that the common talking circuit connecting the two groups of subscribers are divided at armatures II and IIS so that the ordinary service subscribers may complete connections in their own group and talk over conductors 3 and 4 during the time a conversation is being held in the secret service line group over conductors I and 2. After conversation and in response to both secret service subscribers replacing their receivers, relay IllI deenergizes and at armature I I4 disconnects ground from conductor |06 to extinguish the secret service lamps |65. At armature H relay IOI opens the locking circuit of relay |02 which now deenergizes and the equipment in Fig. 2 is now fully restored to normal position.

Having described an established connection between two subscribers in the secret service group a description will now be given of the operations which take place when an ordinary service subscriber calls another subscriber in the same group. This connection may be established during the time a connection exists on the secret service lines. For example, it will be assumed that subscriber OSI desires to call subscriber OS2, and in response to the subscriber at substation OSI removing his receiver, after first ascertaining by means of the busy lamps that the line is idle, a circuit is completed for energizing relays I 03 and |04. This circuit may be traced as follows: From ground, through the lower winding of relay |04, conductor 4, through the calling substation loop to conductor 3, through the upper winding of discriminating relay |03, and through the upper winding of line relay |04 to battery. Relay |03 at armature opens a point in the original energizing circuit of relay |02 to prevent the energization of relay |02 in case the Same is not already energized in a secret service line connection. At armature I 2| short circuits the upper winding of relay |03 to improve the impulsing circuit to render the relay slow to release and to complete a point in the talking circuit, and at armature |22 prepares a point in its own locking circuit. Relays |04 and |05 energize as previously described and relay |05 at armature |24 grounds conductor 53 to light the busy lamps |64 and to complete the locking circuit through the lower winding of relay |03, and at armature prepares the impulsing circuit.

Since the number of subscriber OS2 is 85 the calling subscriber OSI will dial the first digit, or the digit 8. Line relay |04 deenergizes and energizes eight times, and at each deenergization closes the previously traced impulsing circuit for relay |00 and magnet 205. The magnet 205 is therefore operated eight times to step the wipers 203 and 204 of switch M into engagement with their eight bank contacts. Relay |03 is again energized from oiT normal springs 20|. Relay |01 will be temporarily energized over its previously traced circuit only during the time the wiper 204 is passing over its first ve multipled bank contacts, and only in case relay |02 is energized due to the existing connection between two secret service subscribers. When wiper 204 engages its sixth bank contact a circuit is completed for energizing the motor magnet 203 of the connector C as follows: From grounded wiper 204 in engagement with its sixth bank contact, conductor |55, armature |34, conductor |51, twenty-fifth bank contact and wiper 2|2, through the interrupter springs 2 E0, and winding of motor magnet 2|3 to battery. Motor magnet 2I3 energizes and then deenergizes when interrupter springs 2M open its circuit to step the wipers of the connector C into engagement with their iirst bank contacts at which time an automatic stepping circuit for motor magnet 2|3 is completed by wiper 2|2. This circuit may be traced from grounded armature E35, conductor |59 connected to the first to the tenth multipled bank contacts, wiper 2I2, and through the interrupter springs 2|4 and magnet 2|3 to battery. In the same manner as previously described, motor magnet 2|3 automatically steps its wipers until wiper 2|2 no longer engages a grounded bank contact with the result that the wipers of the connector are now stepped into engagement with their eleventh bank contacts because ground has been removed from conductor |58 by the energization of relay |06. From the foregoing it will be seen that the connector is given an automatic stepping movement before the receipt of the second digit whenever the iirst digit is more than ve. This automatic stepping circuit is provided so that a calling subscriber may dial the second digit immediately after the rst without the necessity of waiting for the wipers of the connector to automatically rotate past the first group of lines. Due to this automatic stepping circuit the wipers of the connector are positioned on their eleventh bank contacts before the first impulse of the second digit is received. After transmitting the last impulse of the rst digit series relay |00 deenergizes to prepare the impulsing circuit to motor magnet 2|3 as previously described.

In response to dialling the second digit, or digit 5 in this case, line relay |04 is deenergized and energized five times to transmit ve impulses through the rotary series relay |09 to magnet 2I3 as previously described. Since the wipers of the u the circuitv for the ring cut oftrela'y ||3.

connector C werey resting inl engagement` with their eleventh bankf contacts when the o rst p impulse ofthe second digit is received, the wipers of the-connectorin response to the operation of the motor` magnet-2|3 are operated into engagement with their sixteenthl bank contacts. Since the wipers 203-and 2040i the minor switch lvl are operated into -engagement with their eighth bank contacts andthe wipers ofthe connector are operated into engagement with their sixteenth bank contacts,a ringing'circuit for the individual ringing-lead 05 is therefore, prepared by Wiper 209. Relay |09 is maintained energizedduring the second impulsing period and at armature energizes relay I llwhich locks upat armature |3| and at armatures |34 and |35 opens the auto'- maticstepping'circuit of the connector C. After transmission of the lastV impulse of the second digit line relay |04 is maintained energized and rotary series relay |09 'deenergizes At armature |29 relay |00 energizes ringing relay I||, and the ringing relay II |upon energizing, at armature |30 completes the ringing, circuit and at the vibratingarmY |31 and armature |36 prepares The ringing circuit for ringing the ringer of subscriber OS2 may be traced as follows: Vfrom generator conductor |30,'armature |92, armature |38, rest ing contact and armature m2, amature |41, conductor |50;A wiper 203"in engagement with its eighth bankcontact, wiper 209 in engagement with` its sixteenth bank Contact, over the individual ringing lead 35 of subscriber OS2 through the,` ringer and condenser toi conductor 4 and through the lower winding of liney relay |04 to ground; Afterjthe period 02|?` time forwhich it is adjuste'd'vibrating `arml |31 stcpsvibrating and closes armature |30 long enough to energize slow to operaterin'g cut off relay ||3 which locks at armature as previously'described. At armature |41 relay |`|3 opens the ringing circuit and at armature |48 grounds release conductor |154 to energize the release magnet 200, as Ipreviously described. Release magnet 206 energizes Aand withdraws its holding detent from itsratchet to restore theY Wipers 203and 204 and `ofrfnormal springs 20| and 202 to their normal positions. When off normal springs 20| are-opened in response to the wipers of the switch`M reaching their normal position relay |00 deenergizes and opens the locking circuit of relay ||0`which likewise deenergizes. At armature |21 and itsresting contact relay Ilgrounds conductorV |58 tocomplete the self restoring circuit for operating the motormagnet 2`|3 of the connector C.- Relay H0" at armature I 32Vv opens the circuit of relay Iv which now deenergizes. Motor magnet 2 I3 of the connector C is energized over the multipled bank contacts ||fto-24` inclusive, from grounded conductor |53 to cause the wipers of the connector to be steppedto their normal or twenty-fthposition,. as previously"described.- The deenergization of ringing relay. |I.I at armature |38 opens a iurtherl point ini the ringing circuit Linerelay |04"ismaintained energized as long aseither one of the ordinary' subscribers maintain their receivers oile the switchhook and releaserelayV I 05 is also=maintained` energized from armature |23 tomaintain the release `trunk conductor |03 grounded at armature I 2li-whereby the relays-|03* and ||3 are also maintained in energized position over their respective locking circuits. The ordinary servicesubs'cribers receiveY talking `battery over both windings of line relay ltl'andth'e' heavy talking conductors 3V scribers.

and. 4.- From the foregoing it will be seen that ordinary service subscribers can complete the connection amongst themselves during the time a connection exists between two or more subscribers in the secret service line group, but a secret service subscriber cannot complete a connection in case there is an existing connection between ordinary service subscribers because the line relay |03 is in use by ordinary service sub- After termination of the connection between the subscribers OSI and OS2 and when the receivers are replaced line relays |04 and |05 deenergize as previously described. Atv armature |24 relay |05 disconnects ground from conductor |63 to open the locking circuits of relays |03 and` I I3 which deenergize, and to open the circuit of lamps |64. 'Ihe equipment is now in normal position and may be used on subsequent calls.

From the foregoing it will be seen that after avsecret service subscriber calls another secret service subscriber relays IUI and |02 are maintained energized during conversation and that relay |02 at'armatures IIB and ||9 disconnects the secret service subscriber group from the ordinary subscriber service group. Ordinary service subscribers can call other ordinary service subscribersY in the saine manner as just 'described during the time a connection exists between two` secret service subscribers without interference,` because the common talking circuit is broken at armatures H0 and IIS. Y

It will now be assumed that subscriber SSI desires to be connected with subscriber OSI in the ordinary service group. Responsive to the subscriber at station SSI removing his receiver line relay |04 and release relay |05 energizes in the same manner as previously described. Subscriber` SSI now dials the iirst digit or the digit 6 to deenergize and energize line relay |04 a corresponding Vnumber of times. In the same manner as previously described series` relay |00 and stepping magnet 2050i switch Mare operated and the wipers 203 and 204 of the switch M are rotatedr into engagement with their sixth bank contact. The closure ofthe off normal springs 20| againvv operates relay |06 and the wiper 204 ofv switch Mcloses the circuit for initiating the automatic stepping circuit cfconnector C so that when-the wipers of. the connector C engage their rst bank contacts the stepping circuit from groundedconductor |59 isicompleted to wiper 2'I2 to automatically step the wipers of the connector into engagement with their eleventh bank contact before the second digit is received, as previously described; A

In response'to the subscriberSS| dialling,1 the Y second digit, or the digit 4, line relay |04follows the impulses to operate Vrelay |09 and motor magnet 2 I3, as previously described.y

Relay |09 operates relay "I |0 andl motor magnet 2|3eoperateslthe connector wipers into engagement with their iiiteenthr bank contacts where wiper 201 prepares the-ringing-circuit to the individual lead 04 as previously described. After impulsing, line relay |04 energizes` and series relay |09 4deenergizes and the latter relay at-armature |29'closes the circuit ofringing relay to start' the armA |31 vibrating and to close armature |38 to complete the ringingcircuit.

with its fifteenth bank contact, over the ringing lead 64 individual to subscriber OSI through the ringer and condenser at the substation and from thence over conductor 4 and the lower winding of line relay |04 to ground. After a predetermined time arm |31 stops vibrating to close armature |36 and energize the ring cut-01T relay |I3, as previously described.Y Ring cut-off relay |I3 at armature |45 completes its locking circuit, at armature |41 opens the ringing circuit, at armature |48 grounds release conductor |54 to release the minor switch M and connector C, as previously described, and in this case, at armature |45 does not complete the circuit for energizing relay |02 because the wiper 204 has been rotated past the fifth bank contact and is not, therefore, connected to conductor |49. Release magnet 209 restores the wipers of the switch M to normal and the opening of the off normal springs 20| causes the deenergization of relay |00. At armature |21 relay |00 opens the circuit of relay I|0 which likewise deenergizes and grounds conductor |58 to close the self restoring circuit of the connector C. Motor magnet 2|3 is energized and deenergized in the same manner as previously described by way of the grounded conductor |50 and multipled bank contacts to 24, inclusive, to wiper 2|2 to automatically rotate the wipers of the connector C to their normal position. When subscriber OSI answers, relay |03 energizes in series with line relay |04 and locks at armature |22. At armature |2I relay |03 completes the talking circuit and at armature |20 opens a point in the energizing circuit of relay |02. The talking circuit between the two subscribers includes the talking conductors I, 2, 3, and 4, armatures ||8 and II9 and their resting contacts, and armature I2I of relay |03. yTalking battery is furnished through both windings of relay |04 to both subscribers. After conversation and when both subscribers replace their receivers line relay |04 and release relay |05 deenergizes and the latter relay opens the locking circuits of relays |03 and I I3 to cause their deenergization and extinguish the lamps |04. The apparatus is now in normal position and may be used on subsequent calls.

Calls originating from the OS group to subscribers in the secret service group are completed in a somewhat similar manner obvious from the foregoing description, and it is therefore thought that these detail operations need not be described. Provisions have been made for giving ordinary service subscribers a busy tone indicating that the common talking circuit is busy when an ordinary service subscriber calls a secret service subscriber at a time when there is an existing connection between secret service subscribers. For example, if two secret service subscribers are talking over conductors I and 2, when an ordinary service subscriber desires to call a secret service subscriber, relays IOI and |02, it will be remembered, are energized. Now when the ordinary service subscriber dials the rst digit of a secret service number, the wipers 204 of switch M will ground conductor |49. Since relay |02 is energized at this time because of the existing connection between two secret service lines, relay |01 is energized over the following circuit: from grounded wiper 204 in engagement with any one of its rst ve multipled bank contacts, conductor |49, armature |I6, and through the winding of relay |01 to battery. At armature |92 relay |01 opens the ringing circuit to prevent the application of generator to the called subscribers ringing lead, and at armature |9| prepares a point in a circuit for transmitting a tone to the calling subscriber. When relay III energizes after dialling the last digit of the secret service line, vibrating arm |31 intermittently connects ground to conductor |40 at armature |36. This intermittent connection and disconnection of ground to conductor |40 causes a tone to be transmitted to the calling subscriber by way of conductor |40, armature |9I, to the upper winding of relay |04 from whence the tone is transmitted over the talking conductors 3 and 4 in the well known manner. When the ordinary service subscriber hears this tone such subscriber will replace his receiver and release the apparatus, as previously described.

Code call provisions have also been provided to enable a secret service subscriber or an ordinary service subscriber to call another subscriber by means of code call bells, such as 21|, 212, etc., which are located throughout the establishment at di'erent points. Certain subscribers will be assigned code call numbers for operating the bells in accordance with a corresponding code to enable such subscriber to be located quickly. When the subscriber hears his code he will go to the nearest phone and answer the call.

Assuming now that subscriber SSI has called the ordinary subscriber OSI over the common talking circuit, as previously described, and OSI does not answer, or if some other person does ano swer but does not know where the subscriber OSI is, then the calling subscriber will dial the digit 0 to seize the code call switch and then dial the two digits assigned to this particular subscribers code call number. digit 0 the relays in Fig. 2 and the switch M operate in the same manner as previously described. Since the digit 0 is dialled the wipers 203 and 204 of the switch M are rotated into engagement with their tenth bank contact-s. Wiper 203 prepares a circuit for grounding wiper 2II and wiper 204 in passing over the sixth to the ninth bank contacts closes the previously described automatic stepping circuit of the connector C to cause the connector wipers to be automatically rotated to their eleventh bank contacts. When wiper 204 reaches its tenth bank contact it prepares a circuit for energizing relay I I2. In response to dialling the second digit the relays and connector C operate as before and when the series relay |09 deenergizes after the impulsing period relay III energizes. At armature |39 relay III now completes the circuit for energizing relay I I2 as follows: from grounded wiper 204 in engagement with its tenth bank contact, conductor I5I, armature |39, and through the winding of code call relay |I2 to battery. At armature |4I relay I|2 prepares a new circuit for the ring cut oir relay |I3, at armature |42 grounds conductor |50 and wipers 203 and 2II to mark the first code in the banks of the connector C and code call switch CC, at armature |43 prepares an impulsing circuit for the series relay 255 and the rotary magnet 24| of the switch MI, and at armature |44 grounds conductor |62 to prepare the circuit for the code start relay 252.

The calling subscriber now dials the third digit for operating relay 255 and magnet 24| over the following impulsing circuit: from ground by way of armature |23 and its resting contact, armature I 25 and its working contact, working contact and armature |28, armature |93 and resting contact, armature |43 and. working contact, over conductor IGI, and through the winding of relay 255 and through the winding of In response to dialling the 3 f energize the motor magnet 235.

magnet 24h to battery; Relay 255.at armature 268 opens-the prepared circuit to the code start relay 252, and the magnet 24| operates the wiper 249 one stepior each impulse received to step thewiper 24|)4 of the switch MI in accordance with the second digit. On the rst step of wiper 249-off`normal springsy 243 close and prepare a further point in the circuit for code start relay 252; Slow to release series relay 255 is maintained energized during Athe impulsingperiod and shortly after.A the last impulse is received this relay deenergizes and at Varmature 268 completes theY circuit for energizing the code start relay 252 as follows: from grounded armature |44, .conductor |62, armature 268, off normal springs 243, armature 236 and resting contact, armature 265 and resting` contact, and through thelower winding of vcode start relay 252 to battery. Code start relay 252 is fairly slow to operate and upon operating at armature 259 completes thecircuit for energizing` the motor magnet 235:y of the codecall. switch CC. Motor magnet 235,.upon energizing, .positions its pawl preparatory to stepping the wipers and near the `end offthe armature stroke operates armature 235 to open the circuit to relay 252. Relay 252 isialso-slightly slow to release and after a short intervalf opens the circuit of motor magnet 235 at 259. Motor magnet 235 deenergizes and steps the wipers'one step and at armature 236 again` closes the circuit to relay 252.. Relay 252 energizes over the same circuit as before or from the grounded multipled contacts accessible to wiper 239 to again operate its armature 259 to Motor magnet 235 again interrupts the circuit of relay 252 at, armature 236 and the latter relay again deenergizes to in turn cause motor magnet 235 to deenergize. This interaction betweenmagnet 235 and relayl 252 continues until wiper 232 encounters a grounded bank contactl marked by wiper 2||`of the connector. Assuming that the code ring of the subscriber OSI is 24-2, that is, two rings, a pause, followed by two more rings,

then the last two digits dialled by subscriberV SSI would have been 2 and 2. The `wiper 2|! was therefore rotated into engagementwithrits thirteenth bank contact and wiper 249' of the switch Ml was rotated into engagement with its second banky contact.

Therefore, whenV wiper 232 engages its ninth bank contact a circuit for energizing relay 254 is completed as follows: from ground by way ofthe working contact and armaturev |42, armature |41, conductor |56, wiper 263 l, in engagement with l its tenth bank contact,

wiper 2| in engagement with its thirteenth bank contact, ninth bank contact and wiper 232 of switch CC, through the winding ofrelay 254 and resistance 266 to battery. At armature 264 relay 254 prepares a point in the ringing circuit',

at armature 265 and its resting contact :opens the original energizing circuit of relay `252, and at its working contact closes a circuit .for relay 253` tipled contacts accessible to wiper 239, through armature 261, the winding of relay 254, and resistance 266 to battery. Relay 253 instead of 70;;relay 252 now energizes' from the `rnultipledgrounded contacts engaged by wiper 239; through armature 236` and resting contact, armature 265:

and working contact, and through the winding ofv relay 253 to battery. At armature 262" relay l253;;whic'h is slightly slow.- to operate;` completesz.

the 'circuit forienergizng relay 252 `from the grounded multipled contacts accessible to wiper 230 through its lower Winding. At armature 2591 relay 252 completes the circuit forl energizing the magnet 235. At armature 236 and its working contact magnet 235 completes the ringing circuit for ringing bells 21|, 212, etc., fromv the grounded multipled contacts accessible to Wiper 230, armature. 236 and working contact, armature 264 to code ringing conductor 269-, and

thence through the various bells, such as bellsV 21| and-212, to battery. At armature 236 and its resting contact, magnet 235V opensrthe cir#- cuit. of relay 253 which deenergizesvafter a short interval and at armature 262` opens the circuit of. relay'252. Relay 252 again at armature 259 opens the circuit of magnet 235 which deenergizes rto step the wipers of the code call switch another step and operates its armature 236 to open the ringing` circuit to the code call conductor 269i at its working contact, and at its resting Contact again'completes'the circuit for reen'ergizing slow to operate relay 253. 253 again energizes relay 252-at armature 262; Relay 252 again energizes magnet 235 and this magnet at armature 236` again rings the code call bells and again opens the circuit of relay 253. Fromh the foregoing it will be seen that when wiper 232 encounters thel marked bank contact which designates when the code ring is to start, relay 253 is included in the automatic` stepping circuit of the code call switch by the operation of ringing relay 254 toV decrease the speed of operation of'thefcode call switch and to cause` aV uniform ring to' begiven; Thewipers of the code call switch areoperated in the same manner. as described and each operation of the motor magnet 235 operatesl the code bells until the wiper 232 encountersits eleventh bank 'contact where a circuit is completed for short circuiting relay 254 to cause its deenergization. lThis circuit may be traced from the left hand terminal of vrelay 254, wiper 232 in engagement withits eleventh bank contact, to the right hand. terminal of said relay. Relayl 254 is therefore deenergized and at armature 264 opens the ringing circuit, at armature 265 connects relay 252 in place of relay 253, and at armature 261 opens apoint in'its own locking circuit. `Relay 252 energizes after an interval and at armature 259 again closes the circuit of magnet 235 which also energizes. v This energization of magnet 235 does not cause the code call bells to ring, becausev the vringing circuit is opened at armature 264. Relay 252 deenergizes and causes the magnet 235 to `step the wipers into engagement with their twelfth bank contacts where a circuit is completed for energizing relay 254 as follows: from the grounded multipled contactsfengagedl by wiperv 239, twelfth bank contacts engaged by wiper 232, and through the winding of relay 254 and resistance 2661 to battery. Relay 254 at armature 264 again prepares the ringing cir cuit, at armature 2651 substitutes relay 253 for relay 252, and at armature 261Y completes its own locking circuit. Relays 253 and 252 and magnet 235 operate in the sameV manner asfpreviously by the" wiper 249 of switch MI.

Relay1 since wiper 240 is in engagement. with itssecond.-

bankxcontact, the fourteenth bank. contact ac cessible to wiper 232 4isthe4 markedbankf contact. Therefore, when. Wiper.` 232. is. operatedz-into engagement with this marked bank contact relay 254 is short circuited over the following circuit: from the left hand terminal of relay 254, wiper 232 in engagement with its fourteenth marked bank contact, second bank contact and wiper 240 at switch MI, to the right hand terminal of relay 254. In the same manner as previously described, relay 254 deenergizes and opens the ringing circuit and substitutes relay 252 for relay 253. Relay 252 and magnet 235 cause the wipers of the code call switch to be advanced into engagement with their twentyfourth bank contacts where the circuit is completed for energizing relay 25| as follows: from the grounded multipled contacts accessible to wiper 230 through the off normal springs 243, or from grounded code start conductor |62 by way of armature 258, wiper 23| and twentyfourth bank contact, and through the winding of relay 25| to battery. At armature 250 relay 25| prepares a circuit for the ring cut-off relay II 3, at armature 251 prepares a circuit for the upper winding of relay 252 and at armature 258 completes a locking circuit for itself from grounded code start conductor |62 by way of armature 268, off normal springs 243, and the winding of relay 25| to battery. When the wipers of code call switch CC reach their normal or twenty-fifth position the grounded conductor |62 again energizes relay 252 by way of armature 268, off normal springs 243, armature 236 and resting contact, armature 265 and resting contact, and through the lower winding of relay 252 to battery. The wipers of the code call switch are now rotated through a second cycle in the same manner as previously described to again operate the code call bells in accordance with the code dialled. In the second cycle of operation when wiper 23| encounters its twentythird bank contact 'the circuit prepared for cutoi relay I I3 is completed from grounded wiper 230 and off normal springs 243 or from grounded conductor |62 to wiper 23| in engagement with its twenty-third bank contact, armature 256, conductor |60, working contact and armature I4I, armature |36, and through the winding of ring cut-off relay II3 to battery. This circuit is also connected through armature 251 to the upper winding of relay 252. Ring cut-off relay I I3, upon energizing, at armature |45 completes its locking circuit, at armature |41 disconnects ground from conductor |50 to remove the marking ground from the banks accessible to wipers 203, 2II, and 232, and at armature |48 grounds release conductor |54 to energize release magnets 206 and 242 by way of their off normal springs 202 and 245, respectively. In response to the operation of the release magnets 205 and 242 the minor switch M and MI restore their wipers to their normal positions at which time their respective off-normal springs open. Wiper 204 in restoring opens the circuit of relay |I2 which is now deenergized and off normal springs 20| open the circuit of relay |06 which likewise deenergizes. At armature I 4I relay H2 opens a circuit to the code stop conductor |60, at armature |42 prepares a point in the regular ringing circuit, at armature |43 restores the impulsing circuit, and at armature |44 disconnects ground from code start conductor |62. Relay |06 deenergizes and at armature |21 opens the circuit of relay I| which now deenergizes and grounds conductor |58 to restore the connector as previously described. Relays |04, |05, and

||3 are now the only relays energized in Fig. 2.

In the code call switch in Fig. 3 when ground is removed from conductor |62 and off-normal springs 243 open in response to the restoration of wiper 240 of switch MI ground is disconnected from wiper 23| which is now in engagement with its twenty-third bank Contact with the result that relay 252 deenergizes. The deenergization of relay 252 causes the deenergization of magnet 235 to step the wipers to their twenty-fourth bank contacts. In the same manner as previously described relay 252 and magnet 235 operate to cause the wipers to step to their twentyfth bank contact or normal position. Since at this time ground has been removed from start conductor |62 the wipers of the code call switch come to rest in their normal position and no circuit is completed for relay 252 and relay 25| deenergizes. The code call switch is now in normal position having operated in two complete cycles to ring the code of the called subscriber i twice. When the called subscriber hears his code he will remove the receiver at the nearest telephone and will then be connected over the heavy talking conductors and converse with the calling subscriber. scrib-ers replace their receivers relays |04 and and |I3 deenergize, as previously described, and restore the circuits to normal position.

In the preceding explanation this system has been described as a common talking selective ringing automatic P. A. X., in which any station can call any other station. In certain institutions, such as schools, it is not always desirable to have all stations call all other stations and provisions have been made for operating the system in connection with a so-called master station service system. In this type of system most of the stations can call no one but the master station and the master station then completes the call to the desired party. In Fig. 4 there is shown standard manual substations CI, C2 and C3, which in order to originate a call remove their receivers to automatically signal the master station MS. The master station then by means of the calling device CD controls the apparatus shown in Figs. 2 and 3 to signal the desired subscriber. When the master station service is used the ordinary service substations, such as OSI, OS2, and OS3, are disconnected and replaced by the master station line group comprising substations MS, CI, C2, and C3. The jumpers 43 and 44 are cut to disconnect the ordinary substations from conductors 3 and 4, and the jumpers 45 and 46 are connected as shown to connect conductors 3 and 4 to conductors 5 and 6 of the master station line group. Assuming now that subscriber CI wishes to talk to the subscriber at C3 and in response to the removal of the receiver at CI relay II of the relay group R is energized over the following circuit: from ground, through the lower winding of relay II, conductor 1, through the calling substation loop to conductor 8, and through the upper winding of relay I I, to battery. At armature I5 relay II closes a circuit for energizing relay I2 and a-t armature I6 completes the ringing circuit for operating the ringer at the master station. Relay I2 at armature I1 connects ground to the generator start conductor by way of armature 25 to start the ringing machine shown in Fig. 2 and at armature I8 starts the arm I9 vibrating. Due to the arm I9 vibrating, armature I8 is not permanently closed until after a predetermined time. Since relay I3 is a slow to operate relay, said relay will not operate until arm I9 stops After conversation when both subvibrating and allows amature I8 to be steadily closed. During the time that arm I9 is vibrating, ringing current from generator lead 80 passes over armature 2| and |6 to the ringer at master switch MS to ground. When the arm I9 stops vibrating the ring cut off ,relay I3 is energized from armature I8 and at armature 2| opens the ringing circuit and at armature 20 disconnects ground from the generator start lead |10. The subscriber at the master station MS answers by removing the receiver and after being linformed by subscriber CI that subscriber C3 is desired, the master station will dial the number assigned to the subscriber at C3. In response to the removal of the receiver by the subscriber at station MS relays |03 and |04 energize over the following circuit: from ground through the lower winding of line relay |04, conductor 4, jumper 85, conductor 5, through the master station substation loop to conductor 6, jumper 46, conductor 3, through the upper winding of relay |83, and through the upper winding of relay I 04 to battery. At armature |23 line relay |04 energizes release relay |05 and the latter relay at armature |24 grounds the release trunk conductor |63 to lock relay |03 energized by way of armature |22 and its lower winding. Y

, In response to the master station MS dialling the digits of the called subscriber C3, the wipers of the minor switch M and connector C are operated in the same manner as previously described to select Vthe individual ringing lead of subscriber C3. Relay |09 deenergizes after the last digit is dialled and completes the circuit to energize ringing relay III which at armature |38 completes the ringing circuit over the wipersof switches M and C to the individual lead of subscriber C3 in a manner similar to that previously described. The ring cut ofi relay ||3 cuts the ring off after a predetermined time and restores the minor switch M and the connector C to their normal positions in the same manner as previously described. When the subscriber at C3 answers the two subscribers talk over the heavy talking l conductors 'I and 8 and receive their talking battery through the windings of relay I. When the subscriber at C3 answers the subscriber at master station MS will replace his receiver to release the relays in Fig. 2, as previously described.

In case the secret service subscriber such as SSI is desired by subscriber at CI, the removal of the receiver by subscriber CI causes relays I, l2, and I3 to signal the master station as described. The

subscriber at the master station MS then dials the digits 2 and 2 to operate the minor switch M and connector C to select the individual ringing lead 22 of subscriber SSI and ring such subscriber. When subscriber SSI answers the call -the master station subscriber replaces his receiver and subscriber CI and SSI talk Vover the following talking circuit: the heavy talking conductors I and 2, armatures I|8 and I|9 and their resting contacts, armature |2|, conductors 3 and 4, jumpers 45 and 46, conductors 5 and 6, and conductors 'I and 8. CI subscriber receives his talking battery through the windings of relay II while the subscriber SSI receives his talking battery through the windings of line relay |04. In case the master station subscriber at MS or any manual subscriber such as CI, C2, or C3, is described by any. secret service subscriber, the calling secret service subscriber will dial the digits assigned to the desired subscriber to operate the minor switch-M and connector C to select the individual ringing lead and ring such subscriber Y for substation AI.

thereover in the same manner as previously described.

An explanation will now be given of the direct line service such as shown in Fig. 5 and for this purpose it will be assumed that subscriber A wishes to call subscriber AI. In response to the subscriber at A removing his receiver relay 'Il is energized through the calling subscribers loop over the conductors 5I and 52 and at armature 'I5 completes an energizing circuit for relay 12. At armature 'I6 relay 'II opens the ringing circuit to the ringer at substation A and at armature 'I'I completes the ringing circuit to the ringer at substation AI. Relay "I2, upon energizing, at armature 'it grounds the generator start conductor |10 by way of armature 80 to start the ringing machine shown in Fig. 2, and at armature 'I9 operates the vibrating arm 89 to prepare a circuit for the slow to operate relay 13. The ringing circuit for operating the ringer of substation AI may be traced from generator lead |80, armature 8|, armatures 'I'I and 83, conductor 62, and the ringer and condenser at substation AI, conductor 6| and through the upper winding of relay 'I4 to ground. When arm 80 stops vibrating arm 'I9 lremains closed long enough to energizek slow to operate relay 'I3 and the latter relay at armature 80 disconnect ground from the generator start lead |10 to stop the ringing machine and at armature 8| opens the ringing circuit, When the subscriber at substation AI answers relay 'I4 is energized over the subscribers I and 63 and the substation loop. At armature 82 relay 'I4 closes another circuit for relay 12, at armature 83 opens another point in the ringing circuit to substation AI, and at armature 84 preparesV a point in the ringing circuit to substation A. The talking circuit ex-V tends over the heavy talking conductors and 6I and 53 and 63. The battery feed for subscriber A extends through the windings of relay 1| and the battery feed for the subscriber AI extends through the windings of relay '14. After conversation Vand in response to the subscriber at substation A replacing his receiver, line relay 'II deenergizes and at armature 'I5 opens the original energizing circuit of relay 'I2 which, however, is

now held energized over armature 82 by relay 'I4 in case subscriber AI hasrnot replaced his receiver. At armature 'I6 relay 1I prepares a point in the ringing 'circuit for substation A and at armature 'I'I opens a point in the ringing circuit station AI replaces his receiver line relay 'I4 deenergizes and at armature 82 opens the circuit of relay 'I2 which deenergizes. At armature I3 relay 'I2 opens the circuit of ring cut-olf relay 'I3 kwhich likewise deenergizes and restores the relay group R to normal position. Should the subscriber at substation AI originate the call instead of the subscriber at A practically the same operations will take place as described when A originated the call. The only difference lies in the fact that line relay 'I4 energizes instead of line relay 'II to energize relay l2 so as to automatically ring the called subscriber.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In a telephone system, a first common talking circuit, a rst group of subscriberslines permanently connected to said first common talking circuit, a second common talking circuit normally Connected to said rst common talking circuit,

When the subscriber at subconnected to said second common talking circuit, and means operative only in case a rst group subscriber calls another rst group subscriber for separating said two common talking circuits.

2. In a telephone system, a rst common talking circuit, a first group of subscribers lines permanently connected to said first common talking circuit, a second common talking circuit normally connected to said rst common talking circuit, a second group of subscribers lines permanently connected to said second common talking circuit, means operative only in case a rst group subscriber calls another rst group subscriber for separating said two common talking conductors, and a single subscriber selective signalling means controlled from any of said subscribers lines for selectively signalling any desired subscribers line.

3. In a telephone system, a first common talking circuit, a rst group of subscribers lines permanently connected to said first common talking circuit, a second common talking circuit nor mally connected to said first common talking circuit, a second group of subscribers lines permanently connected to said second common talking circuit, means operative only in case a first group subscriber calls another lirst group subscriber for separating said two common talking circuits, and means operative in case a second group subscriber attempts to call a rst group subscriber during the time a talking connection exists between two first group subscribers over the first common talking circuit for transmitting a tone to the calling second group subscriber indicating the busy condition of the rst common talking circuit.

4. In a telephone system, a common talking circuit, subscribers lines normally connected to said common talking circuit, means for automatically dividing said common talking circuit into two parts, and means for thereafter completing two separate and simultaneous non-interfering conversations between certain of said subscribers lines over the said two divided parts of the common talking circuit.

5. In a telephone system, a common talking circuit, two groups of subscribers lines normally connected to said common talking circuit, means operative only in case a subscriber in the first group calls another subscriber in the rst group for automatically dividing said common talking circuit into two parts, and means for thereafter completing a talking connection between a calling and a called subscriber in the first group over the first divided part of the common' talking circuit and for thereafter completing a non-interfering talking connection between two subscribers in the second group over the remaining part of the common talking circuit in response to one of said second group subscribers calling another second group subscriber.

6. In a telephone system, a common talking circuit, two groups of subscribers lines normally connected to said common talking circuit, means operative only in case a subscriber in the first group calls another subscriber in the first group for automatically dividing said common talking circuit into two parts, means for thereafter completing a talking connection between a calling and a called subscriber in the first group over the rst divided part of the common talking circuit and for thereafter completing a non-interfering talking connection between two subscribers in the second group over the remaining part of the coma second group of subscribers lines permanently mon talking circuit in response to one of said second group subscribers calling another second group subscriber, and means operative in caso a second group subscriber attempts to call a rst group subscriber during the time a talking connection exists between two first group subscribers over the rst part of said common talking circuit for transmitting a tone to the calling second group subscriber indicating the busy condition of the iirst part of the common talking circuit.

7. In a telephone system, a common talking circuit provided with two groups of subscribers stations, means controlled over said circuit responsive to a calling subscriber in either group calling any other subscriber for automatically signalling the called subscriber and for automatically discontinuing the signalling operation after an interval, said common talking circuit completing a talking path between said calling and called subscribers-means automatically operative in case a calling subscriber in the rst group calls another subscriber in the first group for automatically dividing said common talking circuitl into two common talking paths, the rst of which is common to the iirst group subscribers and the second being common to the second group subscribers, and the second common talk' ing path completing a non-interfering talking circuit between second group subscribers independent of said rst common talking path in case a second group subscriber calls another second group subscriber at a time when a talking connection exists between two rst group subscribers over the said first common talking path.

8. In a telephone system, subscribers lines each having an individual ringing lead, an automatic switch, a plurality of wipers in said switch having access to said individual ringing leads, means responsive to a calling subscriber dialling a digit of a called susbcribers number for selecting a particular one of said wipers, means responsive to the calling subscriber dialling anotherdigit in the called number for operating each of said wipers into engagement with an individual subscribers ringing lead, and means for transmitting ringing current over only the selected wiper and the called subscribers individual ringing lead to signal the called subscriber.

9. In a telephone system, subscribers lines each having an individual ringing lead, an automatic switch, a plurality of wipers in said switch having access to said individual ringing leads, means responsive to a calling subscriber dialling a digit of a called subscribers number for selecting a particular one of. said wipers, means responsive to the calling subscriber dialling another digit of the called number for operating each of said wipers into engagement with an individual subscribers ringing lead, means for transmitting ringing current over only the selected wiper and the called subscribers individual ringing lead to signal the called subscriber, and a common talking circuit for completing the talking connection between the calling and called subscribers lines.

10. In a telephone system, subscribers' lines each having an individual ringing lead, an automatic switch, a plurality of wipers in said switch having access to said individual ringing leads, means responsive in case a calling subscriber dials a digit of a called subscribers number for selecting a particular one of said wipers, means responsive to the calling subscriber thereafter dialing another digit of the called number for operating each of said wipers into engagement withL-an rindividual Ysubscribefs "ringing lead,` a code call switch also! accessible to' afpredetermined one of, said wipers, said first means responsive" in case the calling subscriber dials a digit of a,` code callnumber forselecting said'predetermined wiper, said second means thereafter responsive tothe calling subscriber dialing another digit of the code call number for-operating the said predetermined selected wiper. to mark the code call number in the code call VVswitchand for operating the remaining wipers intoengagement with individual subscribers ringingleads, and means foroperatingsaid code'call 'switch to ring a code in accordance with the said marking by said predeterminedwiper.'

1,1. In a telephone system, two groups of` subscribers" lines, Aan automatic switch, a plurality of wipers in said switch, a set of bank contacts for each wiper, a first and a second group of subscribers individual ringing leads corresponding to said first and second line groups terminating in each yset of bank contacts, means responsive to a calling subscriber dialling a digit of a called subscribers number for selecting a particular one of said wipers, means for automatically stepping said wipers past their first groups of individual ringing leads in response to the operation of said rst means in case the digit dialled designates a subscribers line in the second group, and means responsive to the calling subscriber dialling another digit of the called number for operating each of said wipers into engagement with an individual subscribers ringing lead.

12. In a telephone system, two groups of subscrbers lines, an automatic switch, a plurality of Wipers in said switch, a set of bank contacts for each wiper, a rst and a second group of sub'- scribers individual ringing leads corresponding tol said rst and second line groups terminating in each set of bank contacts, means responsive to a calling subscriber dialling a digit of a called subscribers. number for selecting a particular one of said wipers, means for automatically stepping said wipers past their rst groups of individual ringing leads in response to the operation of said first means in case the digit dialled designates a subscribers line in the second groups, means responsive to the calling subscriber dialling another digit of the called number for operating each of said wipers into engagement with an individual subscribers ringing lead, and means for transmitting ringing current over only the selected wiper and the called subscribers individual ringing lead to signal the called subscriber.

13. In a telephone system, a first automatic switch, a second automatic switch, a plurality of wipers in the second switch, a nrst and a second group of subscribers individual leads accessible to each of said wipers, means responsive to a calling subscriber dialling a digit of a called subscribers number for operating the first switch to select a particular one of said wipers, and means for automatically stepping said wipers past their rst groups of individual leads in response to the operation of said rst switch beyond a given position.

14. In a telephone system, a rst automatic switch, a second automatic switch, a plurality of wipers in the second switch, a rst and a second position in said rst switch for each wiper of the second switch, means for directively operating said rst switch to a particular one of said positions to select the corresponding wiper, and means `for automatically operating all the wipers oi. said second "switch in,` response to said rst switch operating beyondlall the said rst selecting positions corresponding to said'wipers.

l5. In" a telephone system, a rst automatic switch, a second automatic switch, a plurality of wipers-in vthe second switch, afirst and a second position in said first switch for each wiper of the second switch, meansrfor directivelyoperating said nrst switch to a particular one of said positions to select the corresponding wiper, means for automatically operating all the wipers of said second switch in response'to: said iirst switch operating beyond' all the saidirst selecting posi- Vtions corresponding to said wipers, and means for thereafter directively operating all the wipers of said second switch. f 1

16. In a telephone system, a first automatic switch, a second automatic switch, a plurality of wipers in the second switch, a first and a second position in said irst switch for each wiper of the second switch, means for directively operating said nrst switch to a particular one of said positions to select the corresponding wiper, means for automatically operating all the wipers of said second switch in response to said first switch operating beyond all the said first selecting positions corresponding to said wipers, a code call switch selectable in case said first switch is directively operated to a particular one of said second positions in a code call, and means for thereafter directively operating the wipers of said second switch to cause the wiper of the second switch corresponding to said particular second code call position to mark a code in the code call switch.

17. In a telephone system, a plurality of automatic subscribers lines including a master station line, a plurality of manual subscribers lines, individual ringing leads for each subscribers line, signalling means controlled from each automatic subscribers line in response to a call for directly selecting the called subscribers individual ringing lead and for signalling such subscriber thereover, means controlled from each manual subscribers line in response to a call for automatically signalling the master station line, said master station line thereafter controlling said rst signalling means to signal the subscriber desired over such called subscribers individual ringing lead, and a common talking circuit connecting all Said subscribers lines for talking purposes.

18. In a telephone system, a plurality of automatic subscribers lines including a master station line, a plurality of manual subscribers lines, individual ringing leads for each subscribers line, signalling means controlled from each automatic subscribers line in response to a call for directively selecting the called subscribers individual ringing lead and for signalling such subscriber thereover, means controlled from each manual subscribers line in response to a call for automatically signalling the master station line, said master station line thereafter controlling said first signalling means to signal the subscriber desired over such called subscribers individual ringing lead, a common talking circuit connecting all said subscribers lines for talking purpose, and means including a code call switch controlled over said common talking circuit by any automatic subscriber for ringing the code call of any desired subscriber.

19. In a telep-hone system, a group of automatic subscribers lines, a group of manual subscribers lines, a master station line, an automatic switch, a plurality of wipers in said switch, manual subscribers individual ringing leads and automatic subscribers individual ringing leads accessible to each of said wipers, means controlled from each automatic line and from said master station line in response to a call for directively operating said switch and Wipers to select any desired subscrbers individual ringing lead and signal such subscriber thereover, means controlled from each manual line in response to a call for automatically signalling the master station line, said master station thereafter controlling said rst signalling means t0 signal the subscriber desired over the called subscribers individual ringing lead, and a common talking circuit connecting al1 said subscribers lines for talking purposes. Y

20. A telephone system comprising two stations normally connected in a direct line system over a talking circuit, a central source of signalling current, a signal for each station, a conductor separate from the talking circuit connected to the signal of each station, means responsive to the removal of the receiver at either station for automatically connecting said signaling current source to the separate conductor line 0f the other station, means controlled over the talking circuit for automatically cutting off said signaling source in response to said other station answering the call, and means for automatically cutting off said signalling source after a predetermined time interval independently of said other station answering.

OSCAR C. LEVY. 

